implement prepend

1 files changed, 8 insertions, 0 deletions

diff --git a/neb/std/lists.py b/neb/std/lists.py
index 1ecbb6d..a49962b 100644
--- a/neb/std/lists.py
+++ b/neb/std/lists.py
@@ -130,3 +130,11 @@ def interpretSortNumbers(symbol, args, env, ns):
     return List(out)
 
 LISTS.register("sort-numbers", Builtin("sort-numbers", interpretSortNumbers, [Arg("list", TypeEnum.LIST)], return_type=Type(":list")))
+
+def interpretPrepend(symbol, args, env, ns):
+    lst = args[0]
+    val = args[1]
+    items = lst.args[:]
+    return List([val] + items)
+
+LISTS.register("prepend", Builtin("prepend", interpretPrepend, [Arg("list", TypeEnum.LIST), Arg("item", TypeEnum.ANY)], return_type=Type(":list")))